The present disclosure relates to the field of electronics. More specifically, this disclosure relates to electronic devices.
Electronic devices are commonly used in a number of applications. Particularly, electronic devices of tamper-resistant type are used to protect them from unauthorized physical intrusions (for example, intended to inspect, alter or disrupt them); a typical example is a crypto-processor dedicated to perform cryptographic operations on board (such as for use in smartcards).
For example, the (tamper-resistant) electronic devices may be designed to prevent (or at least to make it very difficult) the reading of secrets (i.e., sensitive information such as cryptographic keys) stored in the electronic devices from the outside. For this purpose, the electronic devices are provided with security features for detecting any attempts to penetrate them (for example, with microprobes); as soon as any penetration attempt is detected, the electronic devices immediately reset (erase) their sensitive information so as to prevent any unauthorized reading thereof.
Generally, each electronic device includes one or more electronic components to be protected (for example, a microprocessor integrated on a chip), which are encapsulated in an enclosure; the above-mentioned security features may then be based on a security (electric) circuit (or more) that is formed on the enclosure (around the electronic components). The security circuit is very thin, so as to make it very hard (if not impossible) to detect by x-ray inspection. Moreover, the security circuit is arranged in a mesh with a very low pitch, so as to define a sort of (unknown) fence that encloses the electronic components (for example, when arranged along different directions, typically orthogonally, in several overlapping layers). Therefore, by monitoring one or more electric characteristics of the security circuit (for example, its resistance), it is possible to detect any penetration attempt in response to their variation (which may result from a short circuit caused by a conductive probe that reaches two points of the security circuit or from an open circuit caused by an insulating probe that cuts the security circuit).
However, the security circuit may be shunted so as to insulate a portion thereof that is not monitored any longer and then may be used for penetrating the electronic device. Therefore, the security circuit is generally designed in such a way that is difficult to contact it (for example, because it is very fragile and not solderable). In any case, even though these expedients may hinder the probing of the security circuit, they are not able to avoid it at all.